Tubing



C. W. ATTWOOD TUBING A ril 8, 1969 Original Filed July 2, 1962 mvmroxChar/e: W Aim/00d BY M K m-u,

United States Patent 1 3,437,779 TUBING Charles W. Attwood, 4077 2ndSt., Wayne, Mich. 48184 Original application July 2, 1962, Ser. No.206,888. Divided and this application Mar. 14, 1966, Ser.

Int. Cl. B23k 31/06 US. Cl. 219-59 9 Claims ABSTRACT OF THE DISCLOSUREThis application is a division of copending application Ser. No.206,888, filed July 2, 1962 and now Patent No. 3,266,051.

This invention relates to the method of manufacture of geometricallypolygonal tubing and its construction as a new article of manufacturefor load-carrying structural and other purposes, and more particularlyto a new method of tube manufacture incorporating recent welding developments and to new articles manufactured by such method.

New techniques of ultrahigh-frequency resistance welding, such asdescribed in the H. E. Park patent, No. 2,794,108, and the W. C. Rudd eta1. patent, No. 2,818,488, make possible, using the present invention,practical, efficient and high speed production of polygonal tubingrolled continuously from flat strip metal, both ferrous and nonferrous,and its. incorporation into continuous production lines including punchpresses or other perforation producing means.

Heretofore, polygonal tubing has been manufactured by first forming thematerial to round cross-section, welding the edges together, and thenrunning the finished tube through rolls or presses forming it topolygonal cross section. In the present method, the tube is initiallyrollformed to its polygonal shape with the strip edges meeting at alongitudinal corner, and the edges are then welded, preferably using theaforementioned ultrahigh-frequency resistance technique. It is, ofcourse, possible to use other methods of corner welding, but at presentsuch methods are too slow for economical operation.

Other continuous welding, such as those heretofore used to produce roundtubing, cannot profitably be used at present for polygonal tubes forseveral other reasons.

For example, until the present, continuous welding procedures usinghelium or argon shielding was limited by the rate at which heat could beapplied; consequently high production speeds were not possible.High-frequency resistance welding, however, produces only localized heatat higher intensity, thus permitting high speed continuous seam weldingof sections which cannot be fabricated at lower heating rates. Thismethod of welding is equally applicable to ferrous and non-ferrousmetals, including 100 percent pure, high conductivity copper, stainlessand galvanized steel, hot and cold rolled steel, and rare earth metals,using the same welding head. No descaling, flux or filler rod is needed.

In the present welding method, heat is concentrated on the actualedgesof the metal being welded, which reduces distortion and strains inadjacent metal which otherwise 3,437,779 Patented Apr. 8, 1969 occurswith conventional welding and which also requires less pressure.

All of the above makes possible the present concept of roll-formingpolygonal tubing direct from a metal strip with the weldment at onecorner. Heretofore, polygonal tubing was restricted to that having theweldment as a seam on one of the sides, since the round seamed tubing isnot readily bent along the seam. Moreover, the present concept makespossible the rapid production of perforated and/ or knockout tubing byproviding the perforation and/or knock-out forming step prior toforming. Heretofore this was not possible because of the distortionsproduced in the round tube formation and the welding step which destroysthe shape of the perforation and/or dislodges the knockout. Thus,conventional tubing which must be perforated or provided with knockoutsafter fabrication has numerous drawbacks, compared with the presentmethod. Drilling of holes leaves burrs difficult to remove and punchingof, for example, rectangular holes is difficult and expensive as done atpresent. Furthermore, perforations and/or knockouts are not readily madeon that side having the weldment, whereas all sides of the presentcorner-welded tube may be perforated or provided with knockouts.

Perforated sides in polygonal tubing is highly desirable for assemblingwith fittings and/or other tubing to produce structural frames and thelike without welding the parts together. With the present tubing,connections made on any side will not be interfered with by the weldseam which is at the corner. In conventionally manufactured tubing, atleast one side, the side with the seam, cannot be so used forconnections.

The attainment of all the aforesaid advantages in the manufacture ofpolygonal tubing is therefore the primary object of the presentinvention. Other objects and advantages will be readily apparent to oneskilled in the art to which the invention pertains upon reference to theaccompanying drawing illustrating a preferred embodiment of theinvention in which like characters refer to like parts throughout theseveral views and in which:

FIG. 1 is a diagrammatic representation of a preferred production linefor manufacture of tubing according to the method of the presentinvention.

FIG. 2 is a cross-sectional view of the metal strip after perforationtaken substantially on the line 2-2 of FIG. 1.

FIG. 3 is a cross-sectional view of the strip at one forming stage takensubstantially on the line 3-3 of FIG. 1.

FIG. 4 is a cross-sectional view of the tube just prior to seam Weldingtaken substantially on the line 4-4 of FIG. 1.

FIG. 5 is an enlarged fragmentary cross-sectional view of the cornerweldment just after welding.

FIG. 6 is a fragmentary elevational view of a perforated tubing section.

'FIG. 7 is an end view, partially in cross-section, illustrating a setof telescoping tubes, and

FIG. 8 is a fragmentary cross-sectional view of a preferred modificationshowing a knockout.

tions, slugs are punched out completely, but for knockout-forming theslugs are only partially punched out.

The strip 11 is next fed into a power feed roll-forming means 16 afterpassing a special marking press 17. The marking press has a counterwhich counts perforations and may make a special cut-off perforationintermediate selected primary perforations or knockouts depending on thelength of finished tubing desired. The perforations or knockouts must beheld to close module spacing tolerances, and all successive operationsare carefully controlled to reduce distortion so that the finishedtubing will have uniformly and accurately spaced perforations orknockouts positioned at uniform distances from the end of the selectedlength of tubing. Where knockouts have been formed, they are rolled backinto place during the roll forming process so that they act to restoreto the tubing a substantial degree of strength otherwise lost inperforated tubing. To achieve this result, the knockout must, whenreplaced, engage the peripheral edge of the hole.

The rollers 16A of the roll-forming means 16 form the strip directly topolygonal, or in the present case shown, square tubing, forminglongitudinal corners at the lines 11A intermediate the longitudinallyspaced rows of perforations 11B or knockouts 11F which in the presentcase are made on each side of the tubing.

The side edges 11C of the strip 11 are slightly bent so that theirsurfaces will meet on a radial plane to form the fourth or weldmentcorner.

An ultrahigh-frequency welding means 18, utilizing the principles setout in Patents Nos. 2,794,108 and 2,818,488 continuously welds the edges11C together. This or any other welding process which may be usedproduces flash material 11D which protrudes outwardly and inwardly fromthe seam as seen in FIG. 5. The outer flash material is removed bypassing the finished tube through a scarfing means 19. A sizing rollmeans 20 is preferably next provided to assure that the finished tubingis straight, and a cutolf means 21 triggered on the special modulatedperforation made by the marking press rather than on length as iscustomary operates to cut the tubing into the selected sections. Thecutofi is preferably either made to pass through the center of theperforations 11B, or is made, as seen in FIG. 6, such that the dimensionX from the cutolf end 11E to the first perforation center is one-halfthe module dimension Y between adjacent perforation centers. This makesfor standardization through module uniformity.

In actual production, hole to hole or knockout to knockout modulardistance on one-inch centers can be maintained for steel tubing to suchclose tolerance as to keep an overall tolerance in a to 20 foot lengthof, for example, plus or minus inch, with the line running at speeds of100 feet per minute and more.

The roll forming means 16 being power fed, foot per minute speedaccuracy is maintained at plus or minus ;030 tolerance to preventlengthwise distortion.

Only by corner welding can the perforations be initially made on allsides, and by utilizing the present special welding distortions can bereduced sufficiently to make the present method practical.

In ultrahigh-frequency resistance welding, the contact areas are small,voltage higher and current less, producing heat only on the surfaces andeliminating any need for high pressure contact. After welding, thetubing size is within .010 to .015 inch of design.

The present method thus makes possible the high speed manufacture of anew article of manufacture comprising a polygonal perforated tubinghaving a weldment corner. It also makes possible the production of a setof telescoping tubing as shown in FIG. 7.

FIG. 7 illustrates tubes 25, 26, 27 and 28 respectively increasing insize. The exterior of the corners being rounded as shown, the flashmaterial 11D protruding from the inner weldment corners will notinterfere with the insertion of the smaller tubes into the larger as itwould if the weldment were on a side as heretofore has been the case.The sides of concentric tubes are spaced a distance about the same as orless than the protruded flash material, but with the corner welding noproblem of interference exists.

The ability to manufacture a set of such tubes permits their use onewithin the other and with all sides perforated or provided withknockouts on the same modules, the perforations and/ or knockouts andtheir distances from the tubing ends produce close alignment of onetubes perforations and/ or knockouts with the others, as seen in FIG. 7.Uses and versatility of such a set of tubes are limitless, butheretofore it was never possible to manufacture them at high productionrates if at all.

The idea of providing a counter in the line ahead of the forming rollswhich will count perforations and knockouts, along with the provision ofa cut-off means triggered on the count desired rather than length isalso considered unique and produces results heretofore not contemplatedin the production of longitudinal formed members of any cross-sectionalshape, such as angles, channels, and others.

Although only one embodiment of the invention has been disclosed, itwill be apparent to one skilled in the art that various changes andmodifications may be made therein without departing from the spirit ofthe invention as expressed by the scope of the appended claims.

I claim:

, 1. A method of continuous manufacture of polygonal perforated tubingfrom a strip of flat sheet metal, comprising the steps of:

moving said strip longitudinally through a punch press and displacing atleast one row of slugs from the plane of said strip along a line spacedfrom corner lines selected for one side of the tubing,

roll-forming said strip directly to a flat sided tube bent along saidcorner lines with the edges of said strip meeting at a corner of saidtube,

continuously joining said edges together by welding,

and

rounding the outer surfaces of the longitudinal corners of said tube toa radius diminishing the radial thickness of each of said corners by anamount at least equal to the thickness of weld-produced flash materialremaining at the inner weld line of said tube.

2. A method of continuous manufacture of polygonal perforated tubingfrom a strip of flat sheet metal, comprising the steps of:

moving said strip longitudinally through a slug displacing means andproducing a plurality of parallel rows of displaced slugs in said stripalong lines spaced from corner lines selected to form sides of saidtubing,

roll forming said strip directly to flat sided tube form bent along saidcorner lines with the edges of said strip meeting at a corner of saidtube,

contiguously joining said edges together by welding,

rounding the outer surfaces of the longitudinal corners of said tube toa radius diminishing the radial thickness of each of said corners by anamount at least equal to the thickness of weld produced flash materialremaining at the inner weld line of said tubing. 3. A method ofcontinuous manufacture of polygonal tubing from a flat sheet metal,comprising the steps of:

roll forming said strip directly to a flat sided tube form bent alongselected corner lines with the edges of said strip meeting at one cornerline,

contiguously joining said edges together by welding,

rounding the outer surfaces of the longitudinal corners of said tubingto a radius diminishing the radial thickness of each of said corners byan amount at least equal to the thickness of weld produced flashmaterial remaining at the inner weld line of said tube.

4. The method as defined in claim 2 and including the steps of:

moving said strip longitudinally through a means continuously sensingthe number of displaced slugs produced, and

cutting said formed strip into lengths dependent on selected quantitiesof displaced slugs as sensed by said sensing means.

5. The method as defined in claim 1 and in which said edges are joinedtogether by ultrahigh-frequency resistance welding.

6. The method as defined in claim 2 and in which said slugs arecompletely removed from said strip prior to roll-forming.

7. The method as defined in claim 2 and in which said slugs are replacedin the strip during roll-forming.

8. The method of manufacturing formed members as defined in claim 4 andin which said slugs are completely removed from said strip to formlongitudinally spaced perforations.

9. The method of manufacturing formed members as defined in claim 4 andin which said slugs are replaced into the strip after displacementtherefrom to form longitudinally spaced knockouts.

References Cited UNITED STATES PATENTS 2,127,618 8/1938 Riemenschneider29477.7 X 2,641,830 6/1953 Lamb et al. 29-477 2,444,463 7/1948 Nordquist21966 X 2,922,020 1/1960 Andrew 21959 X 3,073,944 1/1963 Yuter 21962RICHARD M. WOOD, Primary Examiner. B. A. STEIN, Assistant Examiner.

